It is often necessary or desirable to transmit a visual image from a point where it originates to some remote location. Frequently electronic techniques, such as typified by closed circuit television, may be advantageously employed in the transmission of visual images to the desired remote location. Such remote presentation of visual information in the form of the desired image is quite conventional, simple, and straight-forward when the original image is erect and stationary. A stationary image may be sensed by an appropriate light sensitive imaging means, such as a vidicon tube, for example, for transmission to any desired point.
However, in some instances it is necessary or desirable that a scene be scanned and a full 360.degree. panoramic view of visual information be transmitted to a remote point. In order to provide such a 360.degree. panoramic view, a suitable optical means such as a rotating mirror tilted at a 45.degree. angle may be employed to translate the 360.degree. scene viewed from its original plane of view to the plane of a light-sensitive means such as a vidicon tube, for instance.
If the image sensing means, such as a vidicon tube, is rotated in synchronism with the rotating mirror, an erect panoramicly panned image, rotating through the full 360.degree., will be presented at the remote imaging means such as a conventional cathode ray tube of the television type. It is however, difficult and inconvenient to rotate the optical imaging means such as a vidicon tube because of the great number of electrical connections and controls associated with such an image sensor.
There are various optical mechanical and/or electromechanical arrangements for providing the maintenance of an erect image at the remote point; these include counter rotating optical wedges, K mirrors, dove prisms, and rotating deflection yokes, in addition to the aforementioned rotation of the image sensor such as a vidicon tube in synchronism with the rotating mirror.
Some of these techniques may be employed best at the image sensor where the rotating image originates, while other techniques are employed at the remote image display or the monitor. For example, it is possible to optically derotate the image just before the focal plane of the image sensor using one of the optical-mechanical techniques previously mentioned such as counter-rotating optical wedges, K mirrors, dove prisms, or rotating deflection yokes. These techniques and expedients may be quite acceptable if there is sufficient space available for the additional optical elements and the necessary servo-mechanism components which are required to be employed in their practice. There is, however, a loss of light transmission in the practice of most of these techniques which, of itself, is quite undesirable.
It is also possible to rotate the deflection assembly of the image sensor such as a vidicon tube by electro-mechanical means in synchronism with the rotating mirror or prism which is employed to sense a panoramic 360.degree. visual scene, for example. However, the use of such techniques may entail even greater problems due to large size, complexity, and the required use of slip rings.
A third but even less efficient technique and means would be to rotate the entire image sensor such as a vidicon tube with the rotating mirror or prism. Although this is a form of simple derotating in theory, its practical implementation would require a substantial amount of power to drive the rotation of the image sensor if 360.degree. rotation were necessary. In addition, slip rings, which introduce unwanted spurious signals or noise, would have to be employed. Moreover, in its practical embodiment and application this technique is bulky in size and cumbersome in that it introduces many undesirable peripheral problems and effects.
On the other hand, it is possible to rotate the deflection assembly by an electromechanical arrangement at the remote visual display such as provided by a remotely placed conventional television tube, for example, to maintain an erect, non-rotating image. Another possibility is the employment of an x,y coordinate rotation performed on the deflection fields produced by the deflection assembly of the remotely positioned cathode ray monitor or display. However, neither of these techniques or expedients is desirable from a human factors standpoint because in the use of either of these latter two methods and techniques the raster pattern of the remote television display tube would rotate to maintain the presentation of an erect non-rotating image.
Accordingly, in a system which has scan generated alphanumeric readout superimposed over the video presentation, the alpha-numeric characters would rotate along with the display raster so that if the raster had to rotate through 360.degree. to maintain an erect non-rotating image of a 360.degree. panoramic scene, the alpha-numeric characters would be rotating through the 360.degree., rendering them virtually unreadable for most of the rotation and distracting from the information contained in the video display presented in erect, non-rotating form.
This would be of particular concern from the human factors standpoint in that it would be most distracting and disconcerting to an observer in the man-machine interface context.
Consequently, there is a need for a technique and system for derotation of a rotating image which satisfies the requirements of space, cost, complexity, and human factors considerations as mentioned hereinbefore. Such a system should be desirably entirely electronic and electrical in its nature and not dependent upon electromechanical moving parts such as rotating deflection assemblies, etc. as were employed in prior art techniques and systems.